Page 55 - rise 2017

Comparison between UV LEDs [6] and UV Fluorescent Lamp [6][7]
UV LEDs UV Florescent Lamp

Light Emit a narrow range of UV light Emit a slightly broader range of UV
Emittance wavelength but at higher light wavelength, but at a lower
concentration and energy than UV concentration and energy than UV
Fluorescent Lamp LEDs
Wavelength Multiple peaks (254nm, 313nm, 404
Characteristic Single Peak (380nm) nm, 437nm, and 546nm)
Power Usage Less power than UV Fluorescent Require more about 110VAC
Lamp about 12VDC
Weight Lighter in weight UV Fluorescent Heavier in weight than LED UV
Lamp
Life Up to 50,000 hours About 10,000 hours of functional use
(Bulbs are not replace) (bulbs are replaced every 2 or 3 month
depending on amount of use)

Problem Statement
Most exposure systems used in educational institutions are exposure systems with Fluorescent UV
lamps or Metal halide lamps. Both systems are very expensive, too wide UV radiations and not
suitable for the sizes of the PCB to be placed on the equipment. This results in a waste of electricity in
the exposure system if the PCB is small in size. This UV exposure system only supports a single side
PCB which has a lot of time to reveal both sides of the PCB. In addition, the timer and buzzer are not
considered as a requirement of the old design of the exposure system which causes a lot of rough
estimates during PCB exposure. These problems raise specific questions needed to be objective in
achieving the goal of this investigation. One major concern that this problem highlighted is the high
cost of UV exposure system. Given the limitations of the research, this problem poses an investigation
on how to build a UV exposure system at a minimal cost. Another problem is how the device can help
minimize energy consumption during the PCB exposure process. Other queries related to the
performance of the device include how it can support a single and double sided PCB, its ability to
guarantee the best exposure time, and how devices can warn PCB fabricators when the exposure time
is over.

Design and Operation Principle
As shown in Figure 2, an UV LED exposure device comprises of a housing with a door in which a
UV LED exposure circuit, a controller, buzzer and a display unit are arranged. A glass plate is
arranged inside the housing above the UV LED circuit with an estimated gap, on which a copper plate
with a transparent film is placed, in such a way that the transparent film is exposed to the UV LED
radiations from the UV LED circuit. The copper plate is a printed circuit board (PCB). The
transparent film has an image or a circuit design layout or a pattern. Upon the continuous exposure to
the UV LED radiation for a certain time period, the circuit design layout is imprinted on the copper
plate. The exposure time is displayed on the display unit. Upon completion of the exposure time, the
buzzer produces sound alert.